Lansweeper pulls monitors from the client machine's registry. It's possible that the problem monitors are not stored in the registry or that they share a serial with another monitor, in which case they'll be overwritten upon scanning. Serials are used as part of internal monitor IDs. It is known that some manufacturers only store partial serials for some of their monitor models, resulting in duplicate serial entries in the registry (and only one monitor entry remaining in the database).
The best way to troubleshoot this issue would be to contact support@lansweeper.com and provide:
- Program Files (x86)\Lansweeper\Service\Errorlog.txt, as present on your Lansweeper server.
- Screenshot of the Config\Display\Monitor section of one problem client machine's Lansweeper webpage.
- Output of this tool for the same problem client machine. Run the tool on the client machine.